|Publication number||US6837285 B2|
|Application number||US 09/864,925|
|Publication date||Jan 4, 2005|
|Filing date||May 23, 2001|
|Priority date||May 23, 2000|
|Also published as||DE60125276D1, DE60125276T2, EP1157859A1, EP1157859B1, US20020007889|
|Publication number||09864925, 864925, US 6837285 B2, US 6837285B2, US-B2-6837285, US6837285 B2, US6837285B2|
|Inventors||Pentti Juhani Eromaki|
|Original Assignee||Nokian Tyres Plc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (22), Referenced by (5), Classifications (10), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present application claims the benefit of Finish Application No. 20001234, filed May 23, 2000.
The present invention relates to pattern blocks in the tread of a tire, comprising a tread layer of one or several rubber materials on the texture of the tire, and pattern blocks separated from each other by wider grooves in this said tread layer, and fine grooves substantially narrower than the said grooves at least in part of these pattern blocks, each of the fine grooves comprising at least one bend or at least one end within the area of the pattern block.
At present, typically very narrow, differently shaped slits, which are also called fine grooves, capillary slits, or lamellae, are used in the patterning of the tread of tires in cars, delivery vans and trucks as well as other similar vehicles, which are meant to be used in winter conditions and which thus have to have a good grip both on ice, in snow and in slush. In distinction from grooves in the tread, which separate the pattern segments to work separately independent from each other, the internal slits in the pattern segments are so narrow that the sections of the pattern segment on two sides affect each other during driving. Such slits have been decreed, for example, in the publications EP-0 881 103 A1 and EP-0 125 437 A1, in which it is suggested that long bending slits be used, the shape of the slits being different at different places of the tread thickness. The purpose of the first publication is to make it possible to provide the pattern segments with a large number of slits and to retain the number and length of these slits also as the tire wears during use. In the latter publication, the shaping of the slits is meant to prevent the tearing of the webs between adjacent slits, which may be caused by deformations in the pattern segments during the use of the tire.
The publication DE-25 49 668 discloses short hook-shaped slits which are arranged in different positions and which do not extend to the grooves between the pattern blocks, but which are found entirely inside the pattern blocks. The publication DE-2 253 717 discloses also hook-shaped, and additionally V-shaped and zigzag-shaped relatively short slits, of which only one is found in each pattern block according to some applications indicated in the figures of the publication; according to some other applications, several such slits may be included in one pattern block so that they are arranged in line in accordance with the principal direction of the slits or in line transverse to the principal direction of the slits. According to the publication, the several slits in the same pattern block are generally placed at a relatively long distance from each other especially when the line direction of the slits is transverse to the principal direction of the single slits. In one alternative the slits in the same pattern block are arranged as extensions to each other so that the slits are not in the least overlapping, but their ends are rather close to each other. The influence of the shapes and positions of the slits is not disclosed in the publication, but according to the publication it is essential that the surface pattern contains sections in the circumferential direction of the tire that differ from each other in relation to the number of the surface profile units and grooves per area unit and/or contour shapes and/or size and/or arrangement. The purpose is here to reduce noise from the tires and to provide sufficient grip on different road surfaces and in different weather conditions, such as in snow and on ice. Both the treads according to the publication DE-25 49 668 and the publication DE-2 253 717 contain very few of these slits, i.e. fine grooves, and the suggested surface patterns of the tread do not provide anywhere near the sufficient grip properties according to the present level of requirements.
The object of the invention is to provide such a tread for the vehicle tire, which provides the tire with good grip on a road surface with ice, slush, or snow, and which retains these grip properties as well as possible also as the tire wears out, i.e. the tread becomes thinner. The second object of the invention is to provide such a tread, also the other driving properties of which are good both as new, i.e. unworn, and as worn, even if the rubber material used for the tread were relatively soft, i.e. flexible rubber material.
One important advantage of the invention is that each pattern block can be provided with the desired big or relatively big number of slits so that the grip of the tire can be made excellent, but however so that the sections of the pattern block separated from each other by slits in an unworn tread are kept sufficiently strongly or rigidly together, thus making the driving behaviour of even a new tire excellent and not too yielding, for example, in the changes of the driving direction, i.e. the tire is not “sluggish”, even as new. Another advantage of the invention is that, as the tire wears down, for example, the effective number of slits remains at least almost unchanged, i.e. the number or the effective length of the slits is not reduced decidedly or to a harmful extent, so that the grip properties remain good in snow, slush, and on ice. This also provides the tread with a roughening or pilling property continuing substantially until the end of the operating life of the tire so that points projecting into the small inequalities of the road surface and thus increasing the grip are generated onto the tread.
The invention is next decreed in more detail referring to the enclosed drawings, in which
Besides the components not decreed in this specification, the vehicle tires filled with air comprise, among others, the carcass 25, which nowadays typically contains a radial texture in the area of the tread, and on top of the carcass a tread layer 20 manufactured of one or several rubber materials. This tread layer 20 comprises pattern blocks 1 separated from each other by wider grooves 21, and at least in part of these pattern blocks fine slits 2 or capillary slits or fine grooves or lamellae (the terminology is not completely established) or simply just grooves 2, which are essentially narrower than the said grooves, each of the slits comprising at least one bend 5 or at least one end 4 within the area A1 of the pattern block. The grooves 21, the pattern blocks 1 and the slits 2 form together with possible circumferential ribs 17 the surface pattern of the tread. The tread grooves 21 refer to grooves, the groove depth H3 of which is sufficiently large and the groove width W4 so large that the side edges 19 of the adjacent pattern blocks 1 separated from each other by the groove do not at least to a substantial extent contact each other during the use of the vehicle tire, i.e. during driving, even during a change in speed and/or direction. Thus, the pattern blocks do not rest on each other more when the tire is stationary than during accelerations, decelerations or changes in direction, but the pattern blocks can elastically deform at least generally independently, irrespective of the other pattern blocks and their deformation. This can be understood from
Things are different when slits 2 included in the pattern block 1 are concerned, the slit width W2 of these slits being designed so small that the different sections of the same pattern block on the opposite sides of the slit 2 rest on each other during a change in speed and/or direction. In this case, the opposite sides 16 a and 16 b of each slit 2 in the pattern block 1 come into contact with each other from a smaller or wider area at least during accelerations or decelerations or changes in direction, and thus the sections in the pattern block separated by the slit/slits, in the tread of the invention the nubs 8, support each other in driving situations including changes. During the said changes in speed and/or direction, the nubs 8 in the tread on two sides of the slit 2 recline in relation to the circumferential surface of the tire in rest condition, and their outer surfaces 22 form the zigzag-shaped or wavelike form, seen in
According to the invention, at least part of the pattern blocks 1 comprises surface tear points 10 between at least two adjacent slits 2. In this specification, the universal reference number 2 is used of the slit in a case when reference is made to the slit in general, and its features are not defined; the specific reference numbers 2 a-2 e are used in a case when reference is made to a slit of a certain type. According to the first principle of the invention, each surface tear point 10 is developed from webs 3 a, 3 b between the end 4 of at least one slit 2 and at least one second slit 2 or its end 4. Alternatively, according to the second principle of the invention, each surface tear point 10 is developed from webs 3 c, 3 d between the bend of one slit 2 and one second slit 2 or its bend 5. In addition, the web width W3 of the said webs 3 a-3 d in the surface tear points 10 is at most five times the slit width W2 of the slit 2 a-2 e, and two adjacent slits 2 a-2 e further restrict between their mutual webs 3 a-3 d within the pattern block 1 nubs 8 with an area A1. Here, the web width W3 refers to the distance between adjacent slits, as can be seen from the Figures. In the surface tear points 10, the webs 3 a-3 d also have a web thickness P3, which is a measure perpendicular to the web width W3, based on the projection of the slit width W2 of the slit to the level parallel to the web width at that point. In the embodiment in
In the surface tear points 10, the web width W3 and the web thickness P3 are dimensioned according to the rubber material or rubber materials of the tread 20 so that, as the tyre is used during driving, the pier or ridge or web 3 a-3 d of the invention tears into a certain depth H1, starting from the respective outer surface 22 of the tread, the tear depth H1 being substantially smaller than the groove depth H3 and the slit depth H2. According to the invention, the tear depth H1 should be at least 0.5 mm and at most 1.5 mm of the outer surface 22 of the tread. Preferably the tear depth H1 is near to 1.0 mm, such as 0.8 mm-1.2 mm. This tearing of the web 3 a-3 d can be understood with the help of
Besides the matters mentioned above, it can be stated about the dimensioning of the said piers or ridges or webs 3 a-3 d that the web width W3 is preferably at most four times the slit width W2, or at most two times the slit width. In experimental checks with a certain tire type it has been found that the tread works in the way referred to above also when the web width W3 of the webs 3 a-3 d is substantially equal to the slit width W2. The web thickness P3 of the said webs 3 a-3 d again is at most three times the slit width W2 of the slit, or at least half of the slit width. In experimental checks with a certain tire type it has been found that the tread works in the way referred to above also when the web thickness P3 of the webs 3 a-3 d is 0.8×-1.5× the slit width W2. Reducing the web thickness to be smaller than the slit width requires special design of slits, not decreed in detail here—their local narrowing —in the surface tear points 10. In this case it naturally has to be noted that the dimensioning of the webs 3 a-3 d depends of the type of the rubber material for the tread 20, especially on the flexibility and tear strength of the rubber material, and of course of the type and size of the tire. As the flexibility, i.e. elasticity of the rubber material increases the shearing stress increases, which would require that the webs be made thicker if the tear strength remained unchanged, and in a reversed case, as the elasticity decreases, the shearing stress decreases, which should make it possible to make the webs narrower. In practice, the situation is rather complicated, because most often the elasticity and tear strength of rubber are not independent from each other. At present it is believed that the dimensions determined above are either right or at least indicative, but because of the large number of effective factors and mutual dependence, smaller or bigger deviations may occur. For achieving sufficient symmetry, it is expediently estimated that the web width W3 and the web thickness P3 deviate from each other at most ±50%. As the present practical values it can be stated that the web width W3 of the webs is at most 1.5 mm and at least 0.3 mm, or the web width is preferably 0.5 mm-1.0 mm and that, respectively, the web thickness P3 of the webs is at most 1.3 mm and at least 0.2 mm, or preferably 0.4 mm-0.9 mm.
The surface tear points 10 decreed above are thus provided onto the tread of a tyre by arranging to it points with small cross-dimensions, to which the stresses caused by the deformations of the tread and especially of the pattern blocks 1 during driving are directed. When forming these surface tear points it is advantageous to utilise the ends 4 of the slits 2 and/or bends 5 of the slits 2, as will be decreed later in connection with certain forms of embodiment. In the surface tear points 10 it is preferable to use relatively sharp bends 5, as in the figures, for directing the stresses decreed above to a sufficiently restricted area, but also somewhat curved bends 5 may be applied. The said bend 5 is alternatively either the angle 5=5 a, the sides of which are formed by the slit, and of which the slit continues as straight or curved sections, or the curve 5=5 b, which continues as straight sections, and/or convex and/or concave sections. The reference number 5 refers to the bend in general, and the reference numbers 5 a and 5 b are only used to individualise the special features of the bend. The design of different bend types will be handled in detail later. At present it is believed to be advantageous that each one of the webs 3 a, 3 c, 3 d forming surface tear points 10 is located on the convex side K1 of the bend 5 in question, as is shown in
For achieving sufficient effect, each pattern block 1 contains at least one row 18 of surface tearing points 10 formed by the webs 3 a-3 d, and thus nubs 8 restricted by slits 2 between them. Each row contains at least two nubs 8. However, it is more preferable to provide the pattern blocks 1 with two or several said rows 18, each of which contains two or several nubs 8. Thus, the pattern block 1 contains preferably altogether at least five nubs 8. The row direction D1 of the rows 18 determined above is transverse to the circumferential direction Tc of the tire, and preferably, the row direction forms the row angle K2 90° and 45° to the circumferential direction, as can be seen from FIG. 1. The nubs have the essential length L1 and width W1 both in the circumferential direction Tc of the tire and in the lateral direction Tw of the tread. Further, the said nubs 8 are found in pattern blocks in the shoulder areas Ts of the tire and in pattern blocks in the direction of the middle parts Tm of the tire from them, such as in the circumferential rib 17 or ribs of the tread, as in the example in FIG. 1. The circumferential webs, such as the middle web, can naturally be left without the slits 2 a-2 e of the invention and without the nubs 8 of the invention. The nubs 8 of the invention, which are in a manner explained above, attached to the adjacent nubs 8 or the other adjacent section of the pattern block with the measure H4=H2−H1 of the webs 3 a-3 s changing along with the wearing down of the tire, work forming the outer surface 22 of the pattern block uneven as the pattern block 1 and the nubs 8 decline, as has been decreed earlier in connection with FIG. 10. Further, during the use of the tire, the nubs 8 wear out more strongly from their edges 14, indicated as dot ticks in
Because the pattern blocks 1 have several nubs 8 of the invention, the area A2 of each nub is thus substantially smaller than the area A1 of the pattern block 1, for example, one third, one fourth or one fifth, or an even smaller share of the area A1 of the pattern block. However, the nubs 8 have to be larger than a certain minimum size both from their area and both dimensions perpendicular to each other in the direction of the outer surface 22. The nubs have to be of such a size and shape that the biggest possible circle to be fitted into or drawn onto the outer surface 22 in the area of slits 2 and surface tear points 10 restricting it, i.e. the circle Y found on the area A2 of the nub and touching the slit 2 restricting it at least in three points—if the nub is restricted by substantially straight slits—or at least in two points—if the nub is restricted by substantially curved slits—has an area A3 which is at least 1.7 mm2, but preferably at least 3 mm2, and typically 5 mm2-12 mm2, when tires of a car are concerned. According to the invention, both measures L1, W1 of the nub perpendicular to each other in the direction of the outer surface 22 do not advantageously deviate too much from each other, but the total area A2 of the nub is preferably at most four or three times the area A3 of a maximum-sized circle drawn inside the nub, or typically at most double compared with the area A3 of the circle, i.e. A2≦4×A3, or A2≦4×A3, or A2=1×A3-2×A3. In tires of a delivery van, the minimum size of nubs 8 is about 1.5 times the values for the car tires, etc., i.e. the area A3 of a maximum-sized circle Y drawn inside the nubs is at least 2.5 mm2 or at least 5 mm2 or 7 mm2-24 mm2, and respectively, the total area of the nubs relates to this area of the circle as above, i.e. A2≦4×A3, or A2≦4×A3, or A2=1×A3-2×A3. In tires of a truck or a bus, the area of the maximum-sized circle Y drawn inside the nubs is about double the values for car tires, i.e. A3 is at least 3 mm2 or at least 8 mm2 or between 15 mm2 and 50 mm2, and further respectively, the total area of the nubs relates to this area of the circle as above, i.e. A2≦4×A3, or A2≦4×A3, or A2=1×A3-2×A3. The maximum size of the nub 8, or the area A2, depends on the size of the tire, being about 40 mm2 in car tires, about 60 mm2 in delivery can tires, and about 100 mm2 in truck tires.
In cases, in which the said bend 5 of the slits is the angle 5 a, its angular value β, i.e. the angular space of the slit sections coming to the angle 5 a, is at least 60° and at most 120°, and preferably, the angular value β for the said angle 5 a is 80°-100°. The radius of curvature R3 for the said angle 5 a is at most three times the slit width W2 of the slit (R3=3×W2) so that it is suitable to be used as a part of the web 3 a, 3 c and 3 d forming the surface tear point 10. It is also naturally possible to form the angle 5 a with a smaller radius of curvature, such as R3=2×W2 or 1×W2. Alternatively, the said bend 5 of the slits 2 is an arc 5 b curving with a relatively large radius of curvature, which extends—in cases, in which the arc 5 b continues as sections 15 a with an unchanged radius of curvature R1—as a single shape to the first curvature χ1, the value for which is at least 150° and at most 210°, or preferably 170°-190°. Alternatively, the arc 5 b extends—in cases, in which the arc 5 b continues as substantially straight sections 15 b—to the second curvature χ2, the value of which is at least 60° and at most 120°, or preferably 80°100°. Alternatively, the arc 5 b extends—in cases, in which the arc 5 b continues as sections 15 c, the radiuses of curvature R2 of which are bigger than the radius of curvature R1 of the said arc 5 b—to the third curvature χ3, the value for which is between the said first and second curvature χ1, χ2.
The fine grooves or slits 2 a and/or 2 b and/or 2 c and/or 2 d and/or 2 e may extend to the one edge 19 or to two opposite edges 19 of the pattern block 1 and open into the grooves 21 between the pattern blocks in these points. These edges 19 of the pattern block, into which the slits 2 possibly extend, are either parallel with the circumferential direction Tc of the tire, or they form at most the angle K1=45° in relation to this.
The surface tear points 10 of the invention and the webs 3 a-3 d between the slits 2, or capillary slits, or fine grooves, generating these, may be used in treads of vehicle tires of any type, irrespective of the shapes of the surface pattern. Of these different tread designs, the surface pattern in
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|US7140411 *||Nov 28, 2002||Nov 28, 2006||The Yokohama Rubber Co., Ltd.||Pneumatic tire having inclined main grooves|
|US7814951 *||Sep 6, 2004||Oct 19, 2010||Bridgestone Corporation||Pneumatic tire having tread including convexly curved fine grooves|
|US7950426||Jun 8, 2007||May 31, 2011||Bridgestone Americas Tire Operations, Llc||Tread blocks having reduced edge stiffness|
|US20040238091 *||Nov 28, 2002||Dec 2, 2004||Susumu Watanabe||Pneumatic tire|
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|U.S. Classification||152/209.18, 152/DIG.3, 152/209.28|
|Cooperative Classification||Y10S152/03, B60C2011/1254, B60C11/12, B60C2011/1245, B60C2011/1213|
|Aug 13, 2001||AS||Assignment|
|Jun 10, 2008||FPAY||Fee payment|
Year of fee payment: 4
|Jun 18, 2012||FPAY||Fee payment|
Year of fee payment: 8